Father did will when he remarried setting up how his assets split between adult children and 2nd wife. Now 2nd wife wants all. Any help?

Is she also in her 80s? Who is your father's medical PoA? Your profile doesn't say that he has dementia, but if you suspect he does, and his medical PoA can't get him to the doctor for an exam, then maybe it's time to call APS and report him as a vulnerable adult being subjected to abuse. If you are able to get into the house you can ask your father if he wants to go for a drive. She can't prevent him since if he is of sound mind he can still do what he wants. At that point I'd keep him out of the house and have him a discussion with him about how to move forward. I would also have your phone with the video record her behavior as evidence. If she knows she's being recorded, she might behave (at least temporarily) and let you in to see him and talk to him.

Perhaps she is the one with the beginnings of dementia or some other cognitive or mental health issue or even a UTI. Does she have any adult children you can contact who may be better positioned to talk to her? "Blended" families are fraught with complex trust issues, especially when it comes to inheritances.

Adult protective services, wellness checks, and a lawyer should all be on the menu. Especially if your father is losing his competency and that is diagnosed. I am assuming your stepmom is POA for healthcare and you may not have access. It is kind of a shame this isn't in a trust, as that would ease protection somewhat, I think. I would see a Lawyer soon rather than later with all evidence you have and you all need to keep a diary on all of this AT ONCE. This will almost certainly all end in court. The diary should be a composition binder without tearouts and with all corrections done by strike through. This must hold up in court. Keep attempting contact.

Is dad competent? If there is any question about his mental status, you would do well to have it documented by his doctor. If #2 is on a rampage, she may take him to an atty to draw up a new will.

Did wife kick you out or dad agreed to it as well? If it was only her, you need to contact an atty to find out about setting up in home visits with dad - similar to a child custody. It's very possible #2 is losing her mind and no longer competent - the changes in her behavior. Don't allow her to keep you out of the home. Someone needs to be observing what is going on in there.

What she wants is irrelevant; the will is the guideline.  Based on your description of the situation, it wouldn't surprise me if she attempts to have him execute a new will or make a codicil to the existing one.  

Is it time for your father to suggest the second wife move on, or out?   It doesn't seem as though she's contributing anything except strife.